Add versions list function

This patch add a function to query the Glance API versions.

DocImpact

Change-Id: I21eeaee3db4ae23f608b68bb319772ac612975b4
Closes-bug: #1511180

glanceclient/v1/client.py

@@ -17,6 +17,7 @@ from glanceclient.common import http
 from glanceclient.common import utils
 from glanceclient.v1 import image_members
 from glanceclient.v1 import images
+from glanceclient.v1 import versions
 
 
 class Client(object):
@@ -37,3 +38,4 @@ class Client(object):
         self.http_client = http.get_http_client(endpoint=endpoint, **kwargs)
         self.images = images.ImageManager(self.http_client)
         self.image_members = image_members.ImageMemberManager(self.http_client)
+        self.versions = versions.VersionManager(self.http_client)